This invention relates to a system and method for deriving energy from a source of relatively warm water, which source, for example, may be a geothermal source. Successful systems have been devised for deriving power from geothermal steam, but potential sources of relatively warm water at temperatures below the boiling point of water are by far more numerous than potential sources of geothermal steam. Such sources of warm water are especially inviting because it is not necessary to deal with hazardous high gaseous fluid pressures. The problem is to provide commercially practical means for utilizing warm water as an energy source.